This invention relates to a method for producing polyester-based combined filament yarn and more particularly it relates to a method for producing polyester-based combined filament yarn by which the polyester combined filament yarn is stably produced with good productivity by heat-treating plural groups of extruded polyester multi-filament yarns under different conditions and then doubling and mixing the filaments.
It is well-known that polyester fibers assuming high bulkiness by carrying out heat treatment are obtained by a method for mutually mixing polyester fibers having a difference in heat shrinkage percentage. That is, the method is to more greatly shrink one of polyester fibers having a higher shrinkage percentage and thereby project the other polyester fibers having a lower shrinkage percentage and impart bulkiness thereto during heat treatment.
Furthermore, the fineness of the single filaments of the highly shrinkable fibers is increased and the fineness of the single filaments of the other low shrinkable fibers is decreased to provide a combined filament yarn, which is then converted into a woven or a knitted fabric and heat-treated to afford a woven or a knitted fabric having a soft surface touch and a handle with stiffness.
Many methods for providing a difference among plural filaments and mixing the filament groups have been adopted in order to afford the polyester combined filament yarn having the difference in heat shrinkage percentage.
For example, JP-A 54-82423 (1979) (hereinafter, JP-A means xe2x80x9cJapanese Unexamined Patent Applicationxe2x80x9d) describes a production method of a combined filament yarn comprising quenching a multi-filament yarn melt-extruded from the same spinneret, then dividing the multi-filament yarn into two filament bundles, applying a spinning oil consisting essentially of water to either one of the filament bundles and applying a spinning oil having a higher boiling point than that of water to the other filament bundle. According to the method, both the filament bundles are drawn while separately carrying out heat treatment of both the filament bundles under the same conditions subsequently to the process and the filaments are then mixed. Thereby, the combined filament yarn obtained by the method exhibits a difference in shrinkage characteristics by a difference in thermal behavior of the spinning oils applied to the respective filament bindles when drawn while being heat-treated.
However, there are problems that the difference in shrinkage percentage among filament bundles cannot sufficiently be increased by the method for imparting the difference in shrinkage characteristics (the difference in boiling water shrinkage percentage) among the filament bundles divided by utilizing a difference in boiling point of the spinning oils applied to the filament bundles during the spinning. As a result, the difference in shrinkage percentage among the filaments of the resultant combined filament yarn is small, and the bulkiness is poor. A satisfactory handle is not obtained.
In addition, JP-A 58-191211 (1983) describes a production method of a combined filament yarn by melt extruding two multi-filament yarns from the same spinning pack, providing a difference between collecting positions of both the yarns, taking off the yarns at a spinning takeoff speed of 4500 m/min or above, producing a difference in air resistance force during the takeoff, mixing the filaments, winding the resulting filament yarn and thereby producing a difference between the two yarns in shrinkage percentage. Furthermore, JP-A 60-126316 (1985) describes a production method of a combined filament yarn by melt extruding two or more multi-filament yarns from the same spinning pack, taking off the multi-filament yarns once so as to produce a difference in spinning speed of either one of the filament yarns from the spinning speed of the other filament yarn, then mixing the filament yarn at a higher spinning speed with the filament yarn at a lower spinning speed, taking off the resulting filament yarn, winding the yarn and producing a difference in shrinkage. The difference in shrinkage percentage of the yarns is obtained; however, neither a thermal stress required to exhibit a sufficient fullness in a woven fabric is produced nor a favorable handle is obtained by the methods.
Further, JP-A 7-243144 (1995) describes a method for production by applying water to one filament group in plural melt-extruded filament groups, keeping the other filament group in an uncollected state without applying water thereto, simultaneously passing the filament groups through heat-treating cylinders respectively set at 150xc2x0 C. or above, taking off the filament groups at a speed of 3000 to 5500 m/min, doubling and mixing the filaments.
In this method, it was surely confirmed that a high shrinkage percentage to some extent was maintained because the filament groups to which water was applied did not receive so much effects of heat in the heat-treating cylinder due to different collecting positions and application of water in advance and that a high elongation was obtained because the filament group was kept in a state without being subjected to drawing and high bulkiness was exhibited by heat treatment. There were, however, problems that a combined filament yarn which was hard to obtain a uniform dyeing finish and had a difference in light and shade close to a state of the colored yarn in so-called sprinkling (unevenness of about 1 cm or above in the yarn longitudinal direction) was merely obtained.
In addition, JP-A 8-209442 (1996) describes a combined filament yarn comprising two filament groups different in heat shrinkage percentage of highly shrinkable filaments and low shrinkable filaments in which the low shrinkable filaments are composed of polyethylene terephthalate and the highly shrinkable filaments are composed of a copolymerized polyethylene terephthalate prepared by copolymerizing a specific amount of three kinds of copolymerization components consisting essentially of isophthalic acid and two kinds of hydroxyethoxyphenols and the difference in heat shrinkage percentage was within the range of 5 to 25%. Although a sufficient difference in heat shrinkage percentage was surely obtained by copolymerizing the third component, it was difficult to say that the resulting polyester combined filament yarn was an inexpensive combined filament yarn excellent in productivity and it was unfavorable because the ability of the highly shrinkable filaments themselves was deteriorated even in aspects of the copolymerization of the third component consisting essentially of the isophthalic acid.
Further, JP-A 58-98418 (1983) describes a textured yarn in which high bulkiness was exhibited by adding another kind of polymer to a base polymer without copolymerization of the third component as the highly shrinkable filaments. In this case, the difference in yarn physical properties after false twisting by a difference from the base polymer was small, and the combined filament yarn was insufficient in softness or the like though sufficient for bulkiness.
As another method, JP-A 4-194010 (1992) and JP-A 9-95816 (1997) describe methods for producing combined filament yarns having a difference in elongation and excellent even in color developing properties by changing the discharge hole diameter of a spinneret, providing a difference in draft and producing a difference between a high draft side and a low draft side in spinneret surface temperature. There are, however, problems that the production cost of the spinneret used was extremely increased in order to exhibit the difference in elongation by the difference in draft.
Market needs for textile products have recently been changed from demands for uniform and homogeneous ones to demands for multikind and diverse products according to an aim of consumers at a higher class and further changed from the small kind mass-production to the production of products having added values of diversified small-quantity production. Therefore, it has been desired to improve the production technique for improving the productivity, suppressing a factor to a cost increase and producing the products having added values while responding to demands for quality and quantity of brands having added values.
It is an object of the present invention to provide a method by which a combined filament yarn, having a great difference in heat shrinkage percentage among respective filaments constituting the combined filament yarn and therefore being excellent in handle, can be produced in a simple process at a low cost when polyester yarns are doubled and converted into the combined filament yarn.
According to the research of the present inventors et al., it has been found that the object can be achieved by a production method of the polyester combined filament yarn by adding a polymer different from a base polymer comprising a polyester component in an amount within the range of 0.3 to 5.0% by weight to the base polymer, melt extruding the resulting composition from the same pack, cooling the extruded filament group comprising polyester multi-filaments once to the glass transition temperature or below, then dividing the filament group into two groups, subjecting one filament group in an opened state to non-contact heat treatment at an atmospheric temperature of 120xc2x0 C. or above, keeping the other filament group in a state without being subjected to the heat treatment and subsequently simultaneously taking off the respective filament groups at a speed of 2500 m/min or above and doubling and mixing the filament groups.
Furthermore, it has been found that a combined filament yarn more improved in bulkiness and good in handle is obtained by regulating the discharge hole diameter of the filaments without being subjected to the heat treatment to 1.5 times or above the discharge hole diameter of the filaments subjected to the heat treatment and/or doubling and mixing the filaments and then carrying out drawing and heat treatment and/or false twisting.